General September Weather

Archive of NZ Weather & Climate
Forum rules
These topics are a read-only archive and may be subject to out-of-date information.

For today's weather discussion head to: New Zealand Weather & Climate
Cyclone Tracy
Posts: 2488
Joined: Thu 07/09/2017 19:25
Location: North Shore, Auckland

Re: General September Weather

Unread post by Cyclone Tracy »

Its rumbling around the Tasman - active multi cell clusters travelling eastward.
You do not have the required permissions to view the files attached to this post.
Richard
Posts: 8612
Joined: Tue 14/07/2009 07:32
Location: Medbury, Inland North Canterbury

Re: General September Weather

Unread post by Richard »

The NW wind that returned mid afternoon killed any chance of showers, but i see there were some weakish cb's to the south and huge smoke cloud near Hanmer. Monday is looking good for a descent amount of rain though
NZ Thunderstorm Soc
Posts: 18895
Joined: Wed 12/03/2003 22:08
Location: Raukapuka Geraldine

Re: General September Weather

Unread post by NZ Thunderstorm Soc »

Nice fine day here with some weak but interesting Cu humulus to the west/NW, but nothing much to "wet your pants" about. ;)
JohnGaul
NZThS
Chris Raine
Posts: 952
Joined: Thu 17/04/2003 11:54
Location: Thornbury

Re: General September Weather

Unread post by Chris Raine »

Tasman sea lively with thunderstorms tonight .See Metservice have put risk of small tornadoes for the West Coast for tomorrow morning
User avatar
NZstorm
Posts: 11333
Joined: Mon 10/03/2003 19:38
Location: Grey Lynn, Auckland

Re: General September Weather

Unread post by NZstorm »

Front due across Auckland early evening today with some heavy squally rain. My expectations for a thunderstorm however are lower now than a day or two ago due to fairly weak lapse rates on the front.

Looking like a good soaking tomorrow for Canterbury. Been a wet season down there for sure.
Richard
Posts: 8612
Joined: Tue 14/07/2009 07:32
Location: Medbury, Inland North Canterbury

Re: General September Weather

Unread post by Richard »

NZstorm wrote: Sun 17/09/2017 07:47

Looking like a good soaking tomorrow for Canterbury. Been a wet season down there for sure.
Some of Canterbury, not here, though we've had the perfect amount to give a good soaking but not too much to be over wet.
Cyclone Tracy
Posts: 2488
Joined: Thu 07/09/2017 19:25
Location: North Shore, Auckland

Re: General September Weather

Unread post by Cyclone Tracy »

Electrical activity is ramping up to the west :smile:
You do not have the required permissions to view the files attached to this post.
Chris Raine
Posts: 952
Joined: Thu 17/04/2003 11:54
Location: Thornbury

Re: General September Weather

Unread post by Chris Raine »

Heavy rain and thunderstorm with small hail 1130-1200 .Got 10mm of rain in 10minutes .Was wondering at one point whether the house was going to be hit by a tornado .Steering at the anemometer at the time, nope only 34 knots there so just a squall- straight line winds going through
User avatar
Tornado Tim
Moderator
Posts: 4920
Joined: Sun 19/10/2008 17:17
Location: Raglan, Waikato / Hillcrest, Hamilton

Re: General September Weather

Unread post by Tornado Tim »

NZstorm wrote: Sun 17/09/2017 07:47 My expectations for a thunderstorm however are lower now than a day or two ago due to fairly weak lapse rates on the front.
Yea those forecasted lapse rates have weakened significantly over the last few days.

Still should be a fairly good chance of a storm tonight. Northland has the best divergence and better lift.

I see Metservice has issued a Severe Thunderstorm Watch - mainly outlining the risk for severe squalls.
Metservice Severe Convection Desk wrote: This watch affects people in the following weather forecast districts:
Northland
Auckland
Great Barrier Island
Coromandel Peninsula
Waikato
Waitomo
Taumarunui
Bay of Plenty
Rotorua
Taranaki

An active front is expected to reach Taranaki late this afternoon and then cross the North Island during the evening. Thunderstorms are likely with and following the front, these thunderstorms will bring heavy rain or showers, strong winds gusting 100 km/h, hail and the risk of a small tornado. There is also a moderate risk that a few of these thunderstorms could become SEVERE, producing damaging winds of 110 km/h or stronger or a damaging tornado.

Wind gusts of this strength can cause some structural damage, including trees and power lines, and may make driving hazardous. If any tornados occur, they will only affect very localised areas.
thunderstormWatchImage.png
You do not have the required permissions to view the files attached to this post.
NZAPStrike.net - NZ Aus Pacific Strike Network
User avatar
NZstorm
Posts: 11333
Joined: Mon 10/03/2003 19:38
Location: Grey Lynn, Auckland

Re: General September Weather

Unread post by NZstorm »

Been a partly cloudy day in Auckland and currently 19C. No sign of any frontal cloud yet. But front showing up well on radar!
Cyclone Tracy
Posts: 2488
Joined: Thu 07/09/2017 19:25
Location: North Shore, Auckland

Re: General September Weather

Unread post by Cyclone Tracy »

Very active squall line now on the west side of the North Island. Just counted around 200 CG's and anvil crawlers in the last 60 minutes. Lift index has been underestimated by most of the models at this point in time IMO. Cloud tops have increased to around -50c on the squall line, probably a few good water spouts will spawn from the current observations.
User avatar
Tornado Tim
Moderator
Posts: 4920
Joined: Sun 19/10/2008 17:17
Location: Raglan, Waikato / Hillcrest, Hamilton

Re: General September Weather

Unread post by Tornado Tim »

Some pre-frontal cells just coming across New Plymouth atm I see, Lightning activity fairly average atm, with a good proponderance of +CG, meaning the charge distribution is getting away from the main cell, most probably due to the Jet.
Cyclone Tracy wrote: Lift index has been underestimated
Frontal lift is usually underestimated by models as the index only takes into account the surface. Better to use B4LLI, MLCAPE and TT in combo rather than use soley SFC based indexes.

Will be interesting to see the progression of the front into tonight.
NZAPStrike.net - NZ Aus Pacific Strike Network
User avatar
David
Posts: 7636
Joined: Sat 18/08/2007 21:02
Location: Howick, Auckland

Re: General September Weather

Unread post by David »

A sudden downpour with the front, rain rate up to 130mm/hr. Thought I heard one distant rumble but not 100% sure.
Image
Orion
Posts: 4210
Joined: Sun 08/08/2010 16:49
Location: Ashburton, Mid-Canterbury, 110m asl.

Re: General September Weather

Unread post by Orion »

Just on phone to my Silverdale Spy, heard several very heavy downpours taking place there while we were speaking.
User avatar
Tornado Tim
Moderator
Posts: 4920
Joined: Sun 19/10/2008 17:17
Location: Raglan, Waikato / Hillcrest, Hamilton

Re: General September Weather

Unread post by Tornado Tim »

The front was a flop Lightning wise, hopefully the beefy showers behind have a bit more spark....
NZAPStrike.net - NZ Aus Pacific Strike Network
Cyclone Tracy
Posts: 2488
Joined: Thu 07/09/2017 19:25
Location: North Shore, Auckland

Re: General September Weather

Unread post by Cyclone Tracy »

Had a couple of sparks here, 16mm and a bit of hail. Some decent gusts on the squall line.
User avatar
03Stormchaser
Moderator
Posts: 4431
Joined: Tue 09/12/2003 12:11
Location: Prebbleton

Re: General September Weather

Unread post by 03Stormchaser »

Steady rain atm. Back from Europe now so will be more active. May also explain why I'm up at 2:47am...

Sent from my VIE-L09 using Tapatalk

NZ Largest Storm Chasing Facebook Pagehttp://www.facebook.com/nzstormchasers
NZ Largest Storm Chase Community https://www.facebook.com/groups/NZStormchasersGroup
NZ Stormchasers TV https://www.youtube.com/@NZStormchasers
User avatar
NZstorm
Posts: 11333
Joined: Mon 10/03/2003 19:38
Location: Grey Lynn, Auckland

Re: General September Weather

Unread post by NZstorm »

Heard a rumble to the west about 5.15am. Looking like a cold day with max 14C and scattered wintry cb.
Razor
Moderator
Posts: 5350
Joined: Fri 10/02/2006 15:14
Location: Halswell, Christchurch

Re: General September Weather

Unread post by Razor »

Certainly wet here. 21mm so far and still steadily bucketing down
Christchurch Rocks
User avatar
shovelopikis
Posts: 239
Joined: Mon 03/06/2013 09:37
Location: Taranaki

Re: General September Weather

Unread post by shovelopikis »

great storms that rolled in yesterday evening. loudest cracks of thunder but overall the last few weeks have had lots of storm days. \:D/
Cyclone Tracy
Posts: 2488
Joined: Thu 07/09/2017 19:25
Location: North Shore, Auckland

Re: General September Weather

Unread post by Cyclone Tracy »

Something big is brewing in my opinion towards the end of September, early October. Antarctic surface temps are dropping like a stone, tropics are holding above average. Keep an eye out on the models for a mid latitude cold core cyclonic gyre in the 960's to 970's hPa to attack NZ in the next few weeks.
You do not have the required permissions to view the files attached to this post.
Richard
Posts: 8612
Joined: Tue 14/07/2009 07:32
Location: Medbury, Inland North Canterbury

Re: General September Weather

Unread post by Richard »

Sounds interesting :-k

Rain has got quite heavy here in the last half hour
User avatar
TonyT
Moderator
Posts: 2947
Joined: Thu 08/05/2003 11:09
Location: Amberley, North Canterbury

Re: General September Weather

Unread post by TonyT »

Cyclone Tracy wrote: Mon 18/09/2017 10:56 Something big is brewing in my opinion towards the end of September, early October. Antarctic surface temps are dropping like a stone, tropics are holding above average. Keep an eye out on the models for a mid latitude cold core cyclonic gyre in the 960's to 970's hPa to attack NZ in the next few weeks.
Cold core systems are usually higher pressure, and that fits better with the current weather intelligence, so I would suggest higher than usual air pressures south of NZ in the next few weeks and frequent breakdowns in the westerly flow over the country.
jamie
Posts: 5907
Joined: Fri 25/02/2011 21:35
Location: Hamilton NZ

Re: General September Weather

Unread post by jamie »

What is MS seeing in regards to tomorrows thunderstorm outlook? I've only peeked at GFS quickly but cant see anything to justify a huge moderate risk area of afternoon buildups.
NZ Thunderstorm Soc
Posts: 18895
Joined: Wed 12/03/2003 22:08
Location: Raukapuka Geraldine

Re: General September Weather

Unread post by NZ Thunderstorm Soc »

26mm of rain since 6am here to midday. Still chucking it down. Street flooded a bit again.
JohnGaul
NZThS